Information storage devices are used to retrieve and/or store data in computers and other consumer electronics devices. A magnetic hard disk drive is an example of an information storage device that includes one or more heads that can both read and write, but other information storage devices also include heads—sometimes including heads that cannot write. A head that can read may be referred to as a “read head” herein, even if it includes other structures and functions such as a transducer for writing, a heater, microactuator, electronic lapping guide, laser diode, etc.
In a modern magnetic hard disk drive device, each head is a sub-component of a head-gimbal assembly (HGA) that typically includes a laminated flexure to carry the electrical signals to and from the head. The HGA, in turn, is a sub-component of a head-stack assembly (HSA) that typically includes a plurality of HGAs, an actuator, and a flexible printed circuit (FPC). The plurality of HGAs are attached to various arms of the actuator.
Modern laminated flexures typically include conductive copper traces that are isolated from a stainless steel structural layer by a polyimide dielectric layer. So that the signals from/to the head can reach the FPC on the actuator body, each HGA flexure includes a flexure tail that extends away from the head along a corresponding actuator arm and ultimately attaches to the FPC adjacent the actuator body. That is, the flexure includes traces that extend from adjacent the head and continue along the flexure tail to electrical connection points. The FPC includes conductive electrical terminals that correspond to the electrical connection points of the flexure tail.
To facilitate electrical connection of the conductive traces of the flexure tails to the conductive electrical terminals of the FPC during the HSA manufacturing process, the flexure tails must first be properly positioned relative to the FPC so that the conductive traces of the flexure tails are aligned with the conductive electrical terminals of the FPC. Then the flexure tails must be held or constrained against the conductive electrical terminals of the FPC while the aforementioned electrical connections are made by ultrasonic bonding, solder jet bonding, solder bump reflow, or anisotropic conductive film (ACF) bonding.
Modern magnetic read heads are trending to include more and more additional structures and functions that require electrical connection. For example, electrical connections to the read head may be required for the read transducer (e.g. a tunneling magnetoresistive sensor), a write transducer (e.g. an inductive writer), a heater for dynamic flying height control, a microactuator for fine tracking control, an electronic lapping guide to enhance control of a head fabrication step, and/or a laser diode to heat a local region of an adjacent disk for so-called heat assisted magnetic recording. However, contemporary flexure tails have very little space in their bonding region for additional conductive layer traces, especially since contemporary flexure tails also include flexure bond pads in the conductive layer.
Certain past flexure tail designs have accommodated an increase in the number of electrical connections by adding a second conductive layer (e.g. a second copper layer) in addition to the needed structural layer (e.g. stainless steel) and the first conductive layer (e.g. the copper layer that includes the flexure bond pads). However, such an addition of a second conductive layer increases the cost and complexity of the flexure tail. Hence, there is a need in the art for a new flexure tail design that can accommodate an increased number of traces in a first conductive layer.